There are four date fields in the North Carolina Maps metadata schema: Date Published (Numeric), Date Published (Display), Date Depicted (Numeric), and Date Depicted (Display). Note that each date is recorded in two different formats:
- Numeric dates contain only numbers, or a range of numbers (for example, "1844" or "1910-1920"). Any additional characters should be reserved for the Display date fields. This field will be searchable, but it will not display to the user.
- Display dates can contain additional, non-numeric characters, enabling the cataloger to show approximate dates or date ranges (for example, "circa 1844" or "circa 1870s" or "between 1914 and 1917").
The date published field captures the date, or date range, that the map was published. Often this is a single date, and is clear from information printed on the face of the map. However, there are many North Carolina maps for which no date is given. In these cases, the cataloger must rely on information from bibliographies, printing styles, known dates of the map creator, contextual information, or anything else that would hint at the date of the map.
This field will record the date or dates that the map depicts. In other words, the date when the information on which the map was based is recorded. This date is sometimes referred to as the "situation date." This is important to note for historic maps, but can be very difficult to determine. However, there are a few easy targets.
Historical maps, illustrating particular places or events in history (often military), are often very clear about the date(s) of the event they depict. For example, the map "Map showing the routes of Lord Cornwallis & Genl. Greene in North Carolina," was known to have been published around 1856, but shows military battles that occurred in the early 1780s. For this map, the following dates would be given:
- Date Published (Numeric): 1856
- Date Published (Display): circa 1856
- Date Depicted (Numeric): 1780-1781
- Date Depicted (Display): 1780-1781
U.S. Coast Survey Maps, and other maps produced by the federal government, often include extensive metadata about the making of the map. The complicated coast surveys were often conducted over a period of several years, resulting in the map that shows an area at different points in time.
But for many maps, the cataloger will have to rely on geographic clues in order to determine the date(s) that the map depicts. One of the best ways to do this is, especially with 19th-century maps, is to look at the development of counties and railroads. For example, a statewide map published in 1855, but which does not include Forsyth County, which was formed in 1849, is clearly based on old information. The table North Carolina Counties: Date Founded is a helpful reference when trying to determine the date a map depicts.